Convertible blower/vacuum units (also referred to herein as “blower/vacs”) are commonly used by homeowners and professionals alike for the removal of debris from yards, driveways, sidewalks, etc. As used herein, a convertible blower/vac is a portable device which can be configured for use as either a debris blower or vacuum. When used as a vacuum, vacuum attachments coupled to a housing of the blower permit leaves or similar debris to be vacuumed into an attached bag or other debris container.
When used in the blower configuration, blower/vacs provide a sweeping action created by the production of a fast moving stream of air generated by a rotating impeller located within the blower housing. The impeller draws air into the housing through an air inlet and exhausts an accelerated air stream through an air outlet. The air stream is typically channeled through a tapered, removable blower tube. In addition to providing a more precisely focused air stream, the tapered blower tube also contributes to an air stream of greater velocity.
Because many blower/vac units are designed for hand-held use, they are often made of lightweight materials and utilize lightweight power sources, e.g., small electric-(battery and corded) and gasoline-powered motors. While applicable to blower/vacs having most any power source, the present invention is particularly advantageous for use with corded electric blower/vacs and the remainder of this discussion will focus on the same.
Although size and weight are criteria to consider in the selection of a blower/vac motor, available power is also a factor. Generally speaking, maximum electric current draw for these and other portable consumer devices may be restricted to ensure conformance with conventional household circuits and available electrical equipment (e.g., extension cords). For example, a typical blower/vac may be designed to operate, within acceptable margins, on a 120 volt (60 Hertz), 15 amp circuit.
Nonetheless, a blower/vac motor designed to draw a particular current load under normal operating conditions, e.g., when operating in blower mode with the blower tube installed, may, under certain circumstances, exceed that load. For example, removal of the blower tube may reduce back pressure in and around the impeller, permitting the motor to spin faster and thus draw additional current.
One solution that addresses this “tube removed” condition is to provide a motor that will produce maximum power, e.g., draw maximum current, when the blower tube is removed. However, such motors will inherently operate at a lower speed, and thus draw less current, when the blower tube is installed. Another solution is to provide a motor that is optimized for blower operation, e.g., operation with the blower tube installed. However, as mentioned above, motors optimized for maximum current draw during blower operation may exceed the maximum desired current load if the blower tube is removed.
While either option is acceptable, a solution that yields the desired current draw, i.e., produces the maximum desired motor speed, with the blower tube installed while preventing excessive current draw when the blower tube is removed, would be advantageous. Moreover, a blower/vacuum that utilizes components (e.g., motor and impeller) configured to provide increased air flow, for a given motor size, would be advantageous.